1. Field of the Invention
The present invention relates to an image forming device, such as a laser printer.
2. Description of the Related Art
Conventional laser printers and other image forming devices that employ an electrophotographic system include developing cartridges that are detachably mounted in the image forming device. Each cartridge includes a toner hopper that accommodates toner and a developing roller used to carry toner stored in the toner hopper. This type of developing cartridge is mounted in the image forming device, such that the developing roller in the cartridge is positioned in opposition to a photosensitive drum. Hence, when toner carried on the developing roller is moved into a position opposite the photosensitive drum, electrostatic latent images formed on the photosensitive drum are developed to form visible toner images, which are then transferred onto a recording sheet by a transfer roller.
Ordinarily, an empty sensor is also provided in this type of image forming device to detect when the toner hopper in the developing cartridge becomes empty. When the sensor detects that the toner hopper is empty, a message is displayed to a user indicating that the cartridge is out of toner, prompting the user to replace the developing cartridge. In response, the user removes the empty developing cartridge currently mounted in the image forming device and installs a new developing cartridge in its place.
Toner used in this type of image forming device is designed to be suitable for specific image forming devices in order to achieve maximum performance. Accordingly, if the user mistakenly mounts a developing cartridge filled with toner that is not appropriate for the image forming device, this inappropriate toner may have an adverse effect on image quality, even if the developing cartridge can be mounted in the image forming device and used to perform printing. If used for a long period of time, the inappropriate toner may invite damage to the image forming device and may cause malfunctions that could render the image forming device inoperable. However, it is not easy for the user to determine whether a certain toner is appropriate for the image forming device.